Comair Flight 5191, bound for Atlanta, Georgia, went down soon after its pre-dawn takeoff on Sunday from Lexington's Blue Grass Airport. Only one crew member is known to have survived the crash.
It was the deadliest US air accident in nearly five years.
Debbie Hersman, a member of the National Transportation Safety Board, said at a news conference that investigators had retrieved the airplane's cockpit voice recorder and flight data recorder, the so-called black boxes, and sent them to Washington for analysis.
A "preliminary review" of the data showed that the plane took off at a bearing consistent with the airport's shorter runway, Runway 26, built for smaller, general aviation planes.
"It is my understanding that (the plane also) went through the perimeter fence," she said.
Ms Hersman, however, refused to be drawn into any speculation.
The tail of the 50-seat Bombardier aircraft remained intact, but the crash site has "a large debris field and it's quite scattered", she added.
Blue Grass Airport administrator Michael Gobb earlier told reporters that the short, 1,036-metre runway was for "daylight only" use by general aviation, meaning it was not lit.
The plane took off before dawn, and meteorologists said the weather was clear.
The airport was fully staffed with air traffic controllers and other personnel, he said.
The Comair Delta connections flight went down about 1.6 kilometres west of the airport, said Comair, a wholly owned subsidiary of Delta Air Lines.
Mike Gobb, the airport's executive director, said the plane had "difficulty on departure."
Asked whether the smaller runway would be sufficient for a plane of this size, Mr Gobb said, "No, it is not."
The names of passengers were not released, pending notification of next of kin.
In Tokyo, the Japanese foreign ministry said it was trying to identify two passengers whose names appeared to be Japanese.
Two officials from the consulate general in New Orleans, Louisiana, have been dispatched to the crash site.
Comair president Don Bornhorst said the crew had flown the plane for some time, and that Comair had purchased it new.
Before the crash, its maintenance record was "clean," he said, with maintenance performed the previous day. More than 21,000 take-offs and 13,500 flying hours were "consistent" with a plane of that age, he said.
The crew also had taken its legally mandated rest before takeoff, he said.
He said that the airline had social workers on the scene to comfort family members.
It was the worst US airline accident since an American Airlines flight in New York killed 265 people two months after the terrorist attacks of September 11, 2001.
Gary Ginn, Fayette County coroner, told reporters that most of those on board died from burns rather than smoke inhalation or trauma.
Meanwhile, Bombardier, the Canadian maker of the CRJ-100 50-seat regional jet, sent a team to the crash site to help the US investigation, Sylive Gauthier, a Bombardier spokeswoman, told news agency AFP.
The 2001 crash in New York killed 260 people on board and five others on the ground. An investigation blamed the vertical stabiliser and rudder.